Amongst antivibration supports of this type, the invention relates more particularly to those which comprise:
first and second rigid strength members suitable for securing to respective ones of the two rigid elements to be united, the second strength member extending perpendicularly to the main vibration axis: PA1 an elastomer body interconnecting the two strength members, said elastomer body having a thick bell-shaped wall which extends and flares from a top secured to the first strength member to a base secured to the second strength member, said wall, seen in section on a plane perpendicular to the main vibration axis, having an outline which has four sides substantially in the form of a rectangle, the elastomer body further including an elastomer projection extending in the center of the thick bell-shaped wall projecting from the top of said wall towards the second strength member, said projection having four side faces each facing a respective one of the sides of the thick bell-shaped wall; PA1 a working chamber defined both by the bell-shaped thick side wall and by a rigid wall secured to the second strength member and forming a counter-abutment for the above-mentioned projection; and PA1 a compensation chamber defined at least in part by a wall that is flexible, and in permanent communication with the working chamber via a narrow channel, the working chamber, the compensation chamber, and the narrow channel all being filled with a liquid. PA1 the narrow central portion of the projection has a first thickness, while each of the end portions of the projection has a second thickness greater than the first thickness, with the difference between the first and second thicknesses being greater than 5 mm; PA1 the area of the projection on a right section perpendicular to the main vibration axis is greater than 150 mm.sup.2; PA1 the two sides of the thick bell-shaped wall situated facing the concave side faces of the elastomer projection are longer than the other two sides of said thick bell-shaped wall; PA1 the second strength member is constituted by a plate which extends in a plane generally perpendicular to the main vibration axis and which has a "support" face, the elastomer body being integral with the flexible wall defining the compensation chamber, and said elastomer body being fixed in leakproof manner to the support face of the second strength member, co-operating therewith to define the working chamber, the compensation chamber, and the narrow channel; PA1 the second strength member includes a projection which projects into the working chamber towards the projection of the elastomer body; PA1 the projection of the elastomer body has a length lying substantially in the range 2.3 cm to 2.7 cm; PA1 each side of the thick bell-shaped wall facing a concave side face of the projection of the elastomer body, is separated from end portions of said projection by a distance which, measured perpendicularly to the main vibration axis, lies substantially in the range 0.8 cm to 1 cm; and PA1 the projection of the elastomer body is of a height measured parallel to the main vibration axis which lies substantially in the range 0.8 cm to 1.2 cm.
Document EP-A-0 646 735 describes an example of such an antivibration support.
Supports of that type give entire satisfaction, however in certain configurations they can present relatively high dynamic stiffness for vibration at high frequency, e.g. at about 640 Hz, thus diminishing the vibration filtering effect at said frequency.